The present invention relates generally to the detection and conversion of high frequency electromagnetic energy to electrical signals and, more particularly, to a method of aligning scintillator crystalline structures and a system of use.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward an object, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam of radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the object. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately results in the formation of an image.
Generally, the x-ray source and the detector array are rotated about the gantry within an imaging plane and around the object. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator.
Typically, a ceramic scintillator of a CT system is formed by a large number of small crystalline structures or crystallites. The chemical compound used to form the scintillator material generally defines a particular crystalline structure or geometrical shape of each crystallite. Regardless of geometrical shape, in some known scintillators, the crystallites are not optimally aligned. In these known scintillators, the orientation of the crystallites is not sufficiently controlled thereby increasing light scattering. Moreover, in known CT systems, the light receiving surface of each crystallite is not parallel to the structure""s light exiting surface, thereby increasing light scattering further and decreasing the overall efficiency of the scintillator detector and the CT system.
It would therefore be desirable to design a scintillator with properly aligned and orientated crystallites that reduces light scattering and improves detector and CT system efficiency.
The present invention provides a detector for a CT system that overcomes the aforementioned drawbacks. The detector includes a scintillator for receiving and converting high frequency electromagnetic energy to light energy. The scintillator includes a plurality of crystallites that are aligned parallel to a high frequency electromagnetic energy beam. Properly aligning the crystallites of the scintillator improves the efficiency of the CT system.
In accordance with one aspect of the invention, a method for orientating crystallites in CT scintillators is provided. The method includes melting a composition configured to convert high frequency electromagnetic energy to light energy into a glass melt. The glass melt is then shaped into one of a number of geometrical configurations depending upon the particular CT system. After shaping the glass melt, crystal seeds are deposited inside the glass melt. The method further includes growing crystallites in the glass melt from the crystal seeds and applying a field to the glass melt while growing the crystallites.
In accordance with another aspect of the invention, a method of CT imaging includes providing a plurality of scintillators forming a scintillator array wherein each scintillator includes a plurality of crystallites. The method further includes the step of aligning the crystallites of each scintillator in a uniform direction to receive high frequency electromagnetic energy from a projection source. The projection source directs high frequency electromagnetic energy toward the scintillator array wherein the high frequency electromagnetic energy is converted to light energy. The method also includes transmitting signals indicative of light energy intensity to a data acquisition system and generating a CT image from the transmitted signals.
In accordance with yet another aspect of the invention, a CT system implementing a plurality of scintillators having a plurality of uniformly aligned crystallites- is provided. The system has a high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the plurality of scintillators. A photodiode array having a plurality of photodiodes and optically coupled to the plurality of scintillators is provided to receive light energy output from the plurality of scintillators. The system further includes a gantry having an opening to receive a subject object.
Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.